In a substrate cleaning apparatus for performing scrub cleaning of a surface of a substrate, such as a semiconductor wafer, with a roll cleaning member, the roll cleaning member needs to be pressed against the substrate under a predetermined pressing load (roll load) during cleaning of the substrate. Generally, the roll load is adjusted at the time of startup operation of the apparatus or at the time of maintenance of the apparatus. However, as described above, only by adjusting the roll load at the time of startup operation of the apparatus or at the time of maintenance of the apparatus, the roll load which is actually applied onto the substrate when the roll cleaning member is pressed against the substrate to clean the substrate cannot be grasped accurately due to variation of the property of the roll cleaning member, a time-dependent change of the roll cleaning member, or the like.
Therefore, there has been known a feedback control of a roll load by constructing a closed-loop control (CLC) system in which, for example, supply pressures of air supplied to an air cylinder used for applying the roll load to a substrate by moving a roll cleaning member up and down are measured and a regulating device is controlled based on the measured values. However, because the supply pressures of air are nothing but alternative property, the supply pressures of air do not precisely indicate the roll load actually applied to the substrate during cleaning of the substrate.
Further, there has been known a feedback control of a roll load by constructing a closed-loop control system in which a pressure sensor such as a load cell for measuring a roll load applied to a substrate by a roll cleaning member is provided in a cleaning apparatus and a regulating device is controlled based on the measured values (see patent documents 1 to 3).
Furthermore, in order to enhance control accuracy of a contact pressure (roll load) applied to the substrate so that the cleaning member can thoroughly follow the deflection of a surface (surface to be cleaned) caused by substrate warpage, there has been proposed a device in which a contact pressure is detected by a load detecting sensor, and an actuating mechanism of a mounting shaft having a distal end to which a cleaning member is attached is controlled based on the detected results (see patent document 4). Also, there has been proposed a device in which while a substrate is cleaned by a cleaning brush incorporating a pressure sensor, a brush pressure detected by the pressure sensor is monitored and a brush pressure control mechanism is controlled so that the brush pressure coincides with a target value (see patent document 5).
As an internal pressure stabilizing apparatus for a fluid pressurization type carrier, there has been known a device in which a pressure value inside a pressure chamber is detected by a pressure sensor, and when the detected pressure value differs from a desired pressure value, a valve of an electropneumatic converter is adjusted to cause an internal pressure of the pressure chamber to coincide with the desired pressure value (see patent document 6). Further, in a polishing apparatus, there has been proposed a load cell installed immediately above a gimbal device (tilting mechanism) of a substrate carrier for holding and rotating a substrate (see patent document 7).